Abstract: Strengthening mechanism for rebar with nitrided ferrotitanium is studied by optical microscopy,scanning electron microscopy and transmission electron microscopy,with HRB335 rebar produced by a domestic steel mill and the rebar containing a certain amount of nitrided ferrotitanium based on HRB335 as raw materials,respectively. Experimental results demonstrate that rebar’s strength and ductility are both enhanced as the nucleation of ferrite grain is promoted and ferrite grain is refined by the precipitation of numerous TiN particles produced in the process of solidification. Precipitates obtained by extraction replica method mainly contain a few composite oxides and Ti（C,N） whose size is usually less than 10 nm with multi-wide distribution. So it is quite feasible to use nitrided ferrotitanium as an alloy element to produce HRB400 hot rolled rebar.